Unfused anterior arch of the atlas (in a child)

Case contributed by Dr Chris O'Donnell


Fell off bike. Neck pain and plain radiographs "inadequate". MRI not available.

Patient Data

Age: 11
Gender: Male

Midline cleft in the anterior arch with sclerotic borders is due to a fusion anomaly rather than fracture. Note associated deficiency of posterior arch (a common accompliment)

Case Discussion

The anterior arch develops from one or more ossification centres which usually appear during the first year of life. Fusion of the anterior arch to the lateral masses forming the neurocentral synchrondrosis, normally occurs by the seventh year of life.

Posterior mid-line clefts of the atlas are common whereas anterior mid-line clefts are much rarer and usually associated with a posterior defect.

It is important to differentiate these defects from Jefferson burst fractures by the presence of smooth corticated margins in contrast to the sharp non-corticated appearance of a fracture.  In addition, developmental anomalies may be associated with an atlanto-axial lateral offset of 1-2 mm if there are both anterior and posterior defects.

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Case information

rID: 29574
Case created: 6th Jun 2014
Last edited: 28th Apr 2017
System: Spine
Inclusion in quiz mode: Included

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